The accumulation of medical evidence in recent years regarding the adverse health implications of high fat diets, principally heart attacks, arteriosclerosis and obesity, has caused consumers to become extremely concerned about their diets. It is estimated that between 70-80% of U.S. adult females follow a weight reducing diet at least once a year. Men are also concerned about their weight and cholesterol levels.
Common obesity is currently one of the most prevalent metabolic problems in the general population. Fats and oils are necessary for balanced nutrition. However, the average consumer simply consumes more than is needed for proper nutrition. It is estimated that lipids constitute about 40% of the total calories in the typical western diet. Fats are consumed directly in meats, spreads, salad oils, and in natural produce such as nuts and avocados. Fats and oils are also consumed as a result of absorption or incorporation in foods during baking and frying. The sharp increase in consumption of fast foods is a major contributor to the increase in the amount of dietary fat since fast foods rely extensively on frying processes employing fats and oils. In addition, the snack food industry uses large amounts of fats and oils in the production of potato chips, corn chips and other snack items.
It is clear that there is an enormous potential market for a fat substitute or fat mimetic that is substantially non-digestible or has reduced caloric value. Replacement of fats in the diet with non-caloric substitutes is a more efficient way of reducing caloric intake than replacing sugar or carbohydrates because, gram for gram, the substitution of non-caloric fat substitutes is more than twice as effective as reducing carbohydrate content with substances such as saccharine or aspartame.
One of the difficulties in eliminating fat from the diet is the fact that fats and oils are all-pervasive in food products. In part, this is because they play an important role in the organoleptic acceptability of food products. In addition to imparting flavor, palatability, and creaminess to foods, lipids provide an essential lubricating action.
Generally speaking, a fat substitute providing fewer calories than a conventional triglyceride must be more resistant towards metabolic energy-releasing processes such as disassimulation and catabolism wherein the fat substitute is broken down into simpler substances.
In addition, the fat substitute must be non-toxic at high levels of ingestion. It must contain no toxic residues or impurities. To the extent that a fat substitute may be partially digested upon consumption, any digestion products must themselves to non-toxic. In general, fat substitutes must be without any serious physiological side effects.
A fat substitute must also have good organoleptic qualities of mouth feel and aroma and must not unacceptably alter the taste of a food composition. In addition, fat substitutes must have appropriate physical properties for use in food compositions. For example, they should be liquids or low-melting solids depending on whether they are to be used as oil or shortening substitutes. The ideal fat substitute will also provide the bulk and volume normally associated with an edible lipid.
For a fat mimetic to be widely useful as a direct replacement for a conventional triglyceride, it must also have a high degree of stability at the elevated temperatures normally employed in the preparation of certain fat-containing food compositions. That is, the physical properties and chemical composition of the fat substitute must not be irreversibly and detrimentally altered by exposure to high temperature when used for frying, cooking, baking, and the like. The ideal fat mimetic will additionally be resistant to oxidative and thermal degradation at such temperatures so that it does not discolor, develop off-flavors or unacceptable aroma, generate volatile decomposition products, smoke, or produce toxic by-products.
Many different types of substances have been proposed for use as fat substitutes in food compositions. For example, U.S. Pat. No. 4,861,613 describes esterified epoxide-extended polyols derived from fatty acids, C.sub.3 -C.sub.6 epoxides such as propylene oxide, and low molecular weight polyols containing three or more hydroxy groups such as glycerin, sugars, and sugar alcohols. While such substances have been generally found to have wide utility as fat replacements, a diet which contains a high proportion of certain of these esterified epoxide-extended polyols can result in problems with anal leakage or diarrhea due to the pronounced resistance of these compounds towards digestion and adsorption.
A number of polysaccharides or modified polysaccharides have also been suggested for use as fat replacements in foods. For example, an aqueous slurry of a modified food starch produced by a controlled acid treatment of corn starch may be shear processed under high pressure homogenization conditions to yield a smooth cream. The cream can reproduce the mouth feel and texture of fat in a variety of food applications (Food Technology, August 1991, p. 262). Another example of a fat-replacing ingredient which is also available commercially is manufactured by touch hydrolysis of rice starch using alpha amylase (Food Technology, August 1991, p. 264). This ingredient can be employed as an aqueous gel or in dry (powder) form. However, many of the polysaccharide-based fat substitutes suffer from one or more pronounced disadvantages which limit their usefulness in the preparation of reduced-fat food compositions. A major limitation is that such substances are generally not useable as fat replacements where the food is exposed to temperatures higher than those normally encountered during baking. Additionally, such substances are non-melting solids or powders and thus cannot be substituted for a conventional liquid or low-melting triglyceride in a frying application. Another drawback which has been noted is that since these polysaccharides require water to simulate the mouth feel and texture of fat, baked goods, frostings, and the like have a tendency to dry out, harden, or become stale fairly rapidly as the water migrates out of the food product. Yet another recognized disadvantage of certain polysaccharide food components is that ingestion of such substances in amounts as low as 30 to 100 grams per day can cause some persons to suffer from gastrointestinal discomfort and diarrhea.